使用Picocli时，如何根据位置参数的值要求位置参数和可选参数

import picocli.CommandLine;
import picocli.CommandLine.IParameterValidator;
import picocli.CommandLine.ParameterException;

public class CustomValidator implements IParameterValidator {
    @Override
    public void validate(String value) throws ParameterException {
        // 根据位置参数的值要求位置参数和可选参数
        if (value.equals("some_value")) {
            throw new ParameterException("位置参数的值要求位置参数和可选参数");
        }
    }
}

import picocli.CommandLine;
import picocli.CommandLine.Command;
import picocli.CommandLine.Parameters;

@Command(name = "myapp", mixinStandardHelpOptions = true)
public class MyApp implements Runnable {
    @Parameters(index = "0", description = "位置参数", validateWith = CustomValidator.class)
    private String positionParam;

    @CommandLine.Option(names = "-o", description = "可选参数")
    private String optionalParam;

    @Override
    public void run() {
        // 执行命令行应用程序的逻辑
    }

    public static void main(String[] args) {
        CommandLine.run(new MyApp(), args);
    }
}